Buoyed by ballot victories in four states in November, they're now on the offensive in two more; wins would mean that more than 20 percent of Americans live in places that have approved same-sex marriage.

Opponents are pushing back hard to make sure that doesn’t happen, even as they express confidence that the nation’s high court will rule in their favor when it weighs in on the Defense of Marriage Act and California’s Proposition 8.

“Everyone is looking at the Supreme Court. What happens then defines a lot of more about what happens next in the fight,” said Brian Brown, president of the National Organization for Marriage.”

“We’re gonna win that and then there’s going to be a state-by-state fight, and our record on that is amazing.”

The scope of any Supreme Court decision is far from clear. They could rule that every American is entitled to the right to same-sex marriage or they could allow states to keep bans on gay marriage or they could do something in between.

In the meantime, gay-marriage advocates are pressing the issue at the state level. In addition to Rhode Island and Illinois, lawmakers in Delaware, Hawaii, Minnesota, New Jersey and Rhode Island reportedly could consider the issue later this year.

“There’s always risk when you go to the Supreme Court. You never want to put all your eggs in one basket,” said Janson Wu, staff attorney at Gay & Lesbian Advocates & Defenders.

Wu has been busy in Rhode Island, where bills to allow gay and lesbian couples to wed were introduced in both chambers of the legislature and where the speaker of the House has promised a floor vote this month.

Both sides agree the measure is likely to pass the House. Wu says he’s “cautiously optimistic” of a win in the Senate, followed by the governor’s signature, while Brown says, “I think we’re going to stop the bill.”

In Illinois, a Senate Committee voted 8-5 late Thursday for a gay-marriage bill, but then delayed a full-floor vote. There may not be action on it for weeks.

Jim Young / Reuters

Mercedes Santos, right, hugs her partner of 21 years, Theresa Volpe, after a vote on a bill to approve gay marriage in a committee hearing at the Illinois State Capital.

Sen. Heather Steans, the sponsor, told the Associated Press that it’s a matter of “when, not if” the measure will pass, with Democrats controlling the Senate 40-19.

“This is never going to be an easy one, but it’s only going to get easier,” Steans said, citing growing acceptance of marriage equality among lawmakers and constituents across the state.

Brown scoffed. “If she had the votes, there would have been a floor vote,” he said. “They called off the session. This is a major victory for supporters of traditional marriage.”

Still, his group isn’t taking any chances.

It vowed to form a state political action committee and spend $250,000 to defeat Republican lawmakers who vote for gay marriage in Illinois, crowing that it helped defeat four GOP state senators who supported the bill that passed in New York.

Nine states, accounting for 15.8 percent of the U.S. population, according to the Human Rights Campaign, have approved gay marriage. A total of 38 states have either a state law or constitutional amendment banning same-sex marriage.

States still up for grabs include New Jersey, where the Legislature approved same-sex marriage and Republican Gov. Chris Christie vetoed it, and where a lawsuit that would force recognition of gay marriage is still pending.

Before the debate in the Garden State is resolved, the Supreme Court will probably have ruled on the two cases it agreed last month to take up. It will hear a challenge to the federal law known as DOMA, which denies federal benefits to same-sex couples, and the challenge to Proposition 8, the voter initiative that banned gay marriage and was overturned by state courts.